Realizing the Long Range Plan at RHIC
When you make things complicated enough, they become simple again.
Paul Sorensen
June 10, 2016
Collective Dynamics
The Phase Transitions in the Early Universe
RHIC is ideally suited to study the phase transition that occurred a few microseconds after the Big Bang
One microsecond after the Big Bang, the universe was filled with Quark Gluon Plasma: Quantum Chromodynamics describes how
that QGP froze into the nuclear matter we are made of today
Region Covered by RHIC Energy Scan
2
Lattice QCD: Borsanyi et.al. arXiv:1007.2580
2
Key Discoveries in Collective Dynamics
Discoveries and theory advances enabled by RHICs flexibility give us a detailed model of the evolution of nuclear collisions
Data can only be described using: • an equation-of-state consistent with first principles QCD calculations • a plasma phase with a viscosity smaller than any other known fluid
The hottest matter ever created is also the most perfect fluid known in nature!
Transverse Slice
4
Emergence of near-perfect fluidity: characterization (η/s(T) for example) and understanding
Can the same fluctuations that could have created the asymmetry between matter and anti-matter during the electro-weak phase transition be measured in the QGP phase in heavy ion collisions (chiral anamoly)?
Breaking of chiral symmetry in QCD generates 99% of the visible mass of the universe. Is chiral symmetry restored in these collisions?
Goals for Collective Dynamics
Quark Gluon Plasma Mapping the phase diagram: At low density, the phase transition between QGP and hadrons is smooth. Is there a 1st order transition and a critical point at higher density?
Probing Chiral Symmetry with Quantum Currents
(GeV)NNs10 210 310
4 1
0×
) O
S-H
SS
(H 0
1
2
0.5 0.4 0.3 0.2 0.1
(GeV)B
µ
Au+Au 30%-60%
BES-I
BES-II
But models with magnetic field-independent backgrounds can also be tuned to reproduce the observed charge separation
charge separation
The chiral anomaly of QCD creates differences in the number of left and right handed quarks.
In a chirally symmetric QGP, this imbalance can create charge separation along the magnetic field
+ -
B=1018 Gauss
a similar mechanism in electroweak theory is likely responsible for the matter/antimatter asymmetry of our universe
observed at all but the lowest energy
General Consistency
6
Chiral Magn. Wave as Predicted
0
0.1
0.2
0.3
0.4
0.025 0.035 0.045
U+U 193 GeV 0-10%∆η>0.025
STAR Preliminary(γO
S -γSS
) × 1
04
v2 {2}
Multiplicity binningSpectator binningSTAR QM12 (1210.5498)
Charge Separation ∝ B not v2
Phys.Rev.Lett. 107 (2011) 052303
charge distribution
Questions of Interpretation Remain
7
Current understanding: backgrounds unrelated to the chiral magnetic effect may be able to explain the observed charge separation
-0.01
0
0.01
0.02
0.03
0.04
0 10 20 30 40 50 60 70
M/2
(γos
- γ s
s)
% centrality
STARBlastWave (σφ=0)
BlastWave
-0.01
0
0.01
0.02
0.03
0.04
0 10 20 30 40 50 60 70
M/2
(γos
- γ s
s)
% centrality
v2 CB (σφ=0)v2 CB
-0.01
0
0.01
0.02
0.03
0.04
0 10 20 30 40 50 60 70
M/2
(γos
- γ s
s)
% centrality
v2c (σφ=0)v2c
-0.01
0
0.01
0.02
0.03
0.04
0 10 20 30 40 50 60 70
M/2
(γos
- γ s
s)
% centrality
v2s (σφ=0)v2s
background model charge separation in Au+Au at 200 GeV
Difficult to draw definitive conclusions without well understood, independent lever arms for B and v2. Better statistics from BESII won’t be enough.
Probing Chiral Symmetry with Quantum Currents
8
Current understanding: backgrounds unrelated to the chiral magnetic effect may be able to explain the observed charge separation
Isobar collisions in 2018 can tell us what percent of the charge separation is due to CME to within +/- 6% of the current signal
4096Zr + 40
96Zr vs. 4496Ru+ 44
96Ru
Background level (%)0 50 100
(R
uR
u-Z
rZr)
γ∆
Re
l. d
if.
in
0
0.05
0.1
0.15
Sig
nif
ica
nc
e
0
2
4
6
8
10
12
14
16
18
case 1
case 2
32
σ5
= 200 GeVNNs
20 - 60%
projection with 400M events
Rel
ativ
e di
ffere
nce
in c
harg
e se
para
tion
(Ru
vs Z
r)
9 9
Models show that higher harmonic ripples are sensitive to the presence of a QGP: v3 goes away when the QGP goes away
Data show v3 is present even at the lowest energies and far stronger than can be explained by non-QGP models
But it disappears at lower energies for Npart<50
t = 0 fm t = 2.5 fm t = 5 fm B. Schenke et.al., Phys. Rev. C 85, 024901
Elliptic n=2 flow (image of an atomic fermi gas)
All harmonic flow (QGP simulation)
Mapping the Phase Diagram: QGP at 7 GeV?
0 100 200 300
0
0.02
0.04
0.06
0.08
0.1
AMPT Default; 7.7 GeV
{2}23vpartN
partN
=200 GeVNN
s 62.4 39 27 19.6 14.5 11.5 7.7
Non-QGP Model
10
)2
(fm
2 sid
e -
R2 o
ut
R
6
8
10
12
0.5 0.4 0.3 0.2 0.1
(GeV)B
µ
= 0.26 GeVT
0%-5%; m
/dy
1dv
0
0.01
10%-40%; net-proton
(GeV)NNs10 210 310
ch,p
p/n
{2}
2 3v
0.04
0.05
0.06
0.07
0.08
>0.2 GeVT
0%-5%; p
Maximum in lifetime?
Minimum in pressure?
Region of interest √sNN≲20 GeV, however, is complicated by a changing B/M ratio, baryon transport dynamics, longer nuclear crossing times, etc. Requires concerted modeling effort: the work of the BESTheory topical collaboration is essential
BESI: Anomalies in the Pressure?
11
Non-monotonic trend observed but statistical precision is limited
The moments of the distributions of conserved charges are related to susceptibilities and are sensitive to critical fluctuations
BESI: Critical Behavior?
Higher moments like kurtosis*variance κσ2 change sign near the critical point
Mapping the region of interest: BES-II
12
0 0.1 0.2 0.3 0.4 0.5
Mill
ion
Eve
nts
10
210
310
7.7
9.1
11.5
14.5
19.6
273962.4
200
(GeV)NNs
Cu
rre
nt
Da
ta S
ets BES-II
0 0.1 0.2 0.3 0.4 0.5
/dy
1dv
0
0.01
0.02net-proton
10%-40% BES-I
10%-15% BES-II
(GeV)B
µ
0 0.1 0.2 0.3 0.4 0.5
ne
t-p
roto
n2
σκ
0
1
2
3
0%-5% Au+Au; |y|<0.5
< 2.0 GeV (Prelim.)T
0.4 < p
BES-II
rapidity width0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
net-
pro
ton
2σ
κ
0
1
2
3
=7.7 GeVNNs
=27 GeVNNs
7.7 GeV BES-II
0 0.1 0.2 0.3 0.4 0.5
Mill
ion
Eve
nts
10
210
310
7.7
9.1
11.5
14.5
19.6
273962.4
200
(GeV)NNs
Curr
ent D
ata
Sets BES-II
0 0.1 0.2 0.3 0.4 0.5
/dy
1dv
0
0.01
0.02net-proton
10%-40% BES-I
10%-15% BES-II
(GeV)B
µ
0 0.1 0.2 0.3 0.4 0.5
ne
t-p
roto
n2
σκ
0
1
2
3
0%-5% Au+Au; |y|<0.5
< 2.0 GeV (Prelim.)T
0.4 < p
BES-II
rapidity width0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
ne
t-p
roto
n2
σκ
0
1
2
3
=7.7 GeVNNs
=27 GeVNNs
7.7 GeV BES-II
More Data RHIC Luminosity Upgrade needed for Low Energies
Better Coverage
BES-II: detector and accelerator upgrades for 2019 and 2020
RHIC Run Plan
13
By 2022, large acceptance BESII detector will never have seen 200 GeV Au+Au
Untapped potential for a broad physics program including longitudinal dynamics complimentary to the jet and Quarkonium program of sPHENIX
2016 2017 2018 2019 2020 2021 2022+-200GeVAu+Au-d+AuEnergyScan
-500GeVp+p-62.4or27GeV?
IsobarZr+ZrandRu+Ru BES-II BES-II FullEnergyAu+Au
2η+
1η
0 1 2 3 4 5
cove
rage
η∆
0
1
2
3
4
5
TPC
iTPC
STAR Forward Upgrades FCS/FTS
at 14.5 GeV
beam
y
No. of Particles Correlated
0 1 2 3 4 5
iTP
C B
oost
0
1
2
3
4
5
Spectra
, Ridgen v
di-leptons
2σκ RP Corr.
CME
4N)δ (RP. Corr.
{4}n v
← di-baryons x11
astrophysical implications
Early Time Dynamics
14
By 2022, large acceptance BESII detector will never have seen 200 GeV Au+Au
Untapped potential for a broad physics program including longitudinal dynamics complimentary to the jet and Quarkonium program of sPHENIX
2016 2017 2018 2019 2020 2021 2022+-200GeVAu+Au-d+AuEnergyScan
-500GeVp+p-62.4or27GeV?
IsobarZr+ZrandRu+Ru BES-II BES-II FullEnergyAu+Au
Early Time Dynamics
15
By 2022, large acceptance BESII detector will never have seen 200 GeV Au+Au
Untapped potential for a broad physics program including longitudinal dynamics complimentary to the jet and Quarkonium program of sPHENIX
2016 2017 2018 2019 2020 2021 2022+-200GeVAu+Au-d+AuEnergyScan
-500GeVp+p-62.4or27GeV?
IsobarZr+ZrandRu+Ru BES-II BES-II FullEnergyAu+Au
Current Measurements
16
By 2022, large acceptance BESII detector will never have seen 200 GeV Au+Au
Untapped potential for a broad physics program including longitudinal dynamics complimentary to the jet and Quarkonium program of sPHENIX
2016 2017 2018 2019 2020 2021 2022+-200GeVAu+Au-d+AuEnergyScan
-500GeVp+p-62.4or27GeV?
IsobarZr+ZrandRu+Ru BES-II BES-II FullEnergyAu+Au
Temperature Dependence of η/s
17
By 2022, large acceptance BESII detector will never have seen 200 GeV Au+Au
Untapped potential for a broad physics program including longitudinal dynamics complimentary to the jet and Quarkonium program of sPHENIX
2016 2017 2018 2019 2020 2021 2022+-200GeVAu+Au-d+AuEnergyScan
-500GeVp+p-62.4or27GeV?
IsobarZr+ZrandRu+Ru BES-II BES-II FullEnergyAu+Au
18
RHIC provides access to emergent phenomena of QCD: • Hottest man-made temperature: 300k times hotter than the center of the sun • Data shown to prefer an Equation-of-State consistent with lattice QCD • The QGP created at RHIC is the most perfect liquid ever known • Exploratory scan finds QGP and intriguing behavior below 20 GeV
Following this progress we want to make measurements needed • to define the phase structure in the QCD phase-diagram (critical point?) • study the chiral properties of the QGP • map the T dependence of η/s and other transport properties
In 2018: Isobar collisions will provide definitive evidence on the chiral magnetic effect in 2019-2020: Detector and accelerator upgrades will provide key abilities in the search for a critical point Extended coverage intended for BESII opens up many opportunities for a diverse program in 2022+
Steps toward fulfilling the promise of RHIC
Thanks
BESI: Do We Create QGP at Lower Energies?
The minimum εcτ for QGP formation is between 0.6-1.8 GeV/fm2
BES-I exploratory scan was carried out to shed light on this question
Energy density measurements from exploratory scan: BES-I 2010-2014
21
A. Adare et al. Phys. Rev. C 93, 024901
Head-on Collisions Npart~350
Grazing Collisions small Npart
well above
too close to call
22 22
Models show that higher harmonic ripples are very sensitive to the existence of a QGP phase
v3 goes away when the QGP phase disappears
← n=2 →
J. Auvinen, H. Petersen, Phys. Rev. C 88, 64908
t = 0 fm t = 2.5 fm t = 5 fm B. Schenke et.al., Phys. Rev. C 85, 024901
Elliptic n=2 flow (image of an atomic fermi gas)
All harmonic flow (QGP simulation)
Do We Create QGP at Lower Energies?
23 23
10 210 310
0.04
0.06
0.08
0.1
0.12
0.14
3−10×
ch,PP/n{2}23v
(GeV)NNs
0-5% 10-20% 30-40% 50-60%
Higher energy collisions producing more particles and higher pressure should more effectively convert fluctuations into v3.
Deviations from that expectation could be indicative of interesting trends like a slowing of the speed of sound. What does v3
2/Nch look like?
Critical Behavior: Anomalies in the Pressure?